Safety parameters and stability diagram of hydroxylamine hydrochloride and sulphate

The thermal instability of hydroxylamine (HA) poses severe concerns in the process industry, while preventive and mitigative strategies are required to reduce the frequency and magnitude of associated decomposition phenomena. From this perspective, formulating an aqueous solution or using derived salts could be a solution for risk reduction. Nevertheless, the effect of HA-derived salt addition on HA/water solutions has yet to be reported in the literature. For this reason, the scope of the present work is to examine experimentally whether salt addition can reduce the occurrence and severity of HA thermal degradation. Samples containing HA and hydroxylamine sulphate (HAS) or hydroxylamine hydrochloride (HH) were analysed. During the experimental campaign, a calorimeter was used for the assessment of reaction kinetic, thermodynamic, and onset features. The determined parameters were used for safety purposes to understand the related thermal hazards and to provide stability diagrams. The results show, under certain conditions, that the type and amount of HA-derived salt determines an attenuation of the decomposition of HA/water solutions. Moreover, increasing the amount of salt enhances the susceptibility to decomposition of the HA/water solution, while lower salts content could help stabilise the HA mixtures. According to the developed stability diagram, an inherently safe zone for reaction or storage has been established. Eventually, the proposed structured approach can be intended as a strategic procedure to involve the reaction parameters gathered, which is helpful for drawing general guidelines for establishing safer processes and reaction conditions.